The present invention refers to a lining device for a plate heat exchanger according to the preamble of claim 1, a plate heat exchanger according to the preamble of claim 8, and a method for manufacturing a plate heat exchanger including a package with heat transfer plates and an end plate, which has an outer side and an inner side facing the plate package and at least a porthole.
It is known to provide the portholes of the end plates of a plate heat exchanger with a lining. According to a conventional method, a starting material is manufactured, which consists of a deep-drawn pipe portion and a flange portion extending around the pipe portion and substantially radially outwardly from the pipe portion at its one end. The other end of the pipe portion is introduced into and through the porthole of the end plate so that the flange portion abuts one side of the end plate. Thereafter, the other end of the pipe portion is bent outwardly so that it forms a flange abutting the other side of the end plate. Such a lining has certain disadvantages. The manufacturing of the starting material is performed in several steps with intermediate heat treatment. During certain conditions, problems can occur with the quality of the bent flange due to formation of cracks. The mounting of the lining is performed in several steps.
SE-B-456 856 discloses a lining for a porthole of a plate heat exchanger. The document discloses two embodiments. The first embodiment, which is described most closely, corresponds to the conventional technique described above. The second embodiment refers to a lining divided in two parts with a first part and a second part. The first part is manufactured of a sheet metal and has a substantially cylindrical pipe portion and a flange portion extending outwardly from the pipe portion. The second part is also manufactured of a sheet metal and has a substantially cylindrical pipe portion and a flange portion extending outwardly from the pipe portion. The pipe portions are introduced in the porthole so that an area is formed where said pipe portions overlap each other. The pipe portions are connected to each other by welding but it does not appear how the weld joint extends.
U.S. Pat. No. 4,482,089 also discloses different embodiments of linings for a porthole of a plate heat exchanger. Also in this case, one embodiment corresponds to the conventional technique described above. Another embodiment refers to a lining manufactured of a pipe portion, which is introducible in a porthole. A flange is welded at each end of the pipe portion.
The object of the present invention is to overcome the problems mentioned above and to provide an improved lining device or a porthole of an end plate. In particular, it is aimed at a lining device which may be manufactured in an easy manner and which has an improved quality.
This object is obtained by the lining device initially defined, which is characterised in that the material thickness of the first part is larger than the material thickness of the second part at least at said overlapping area.
Since no deformation of the material takes place in the two parts during the mounting of such a lining device, the risk of formation of cracks of the inner abutment portion is substantially reduced.
Since the material thickness of one part is larger than the material thickness of the other part at least at said overlapping, i.e. the material thickness of at least the one pipe portion is larger than of the other pipe portion, the risk of contamination of the material in the proximity of the weld joint and in the transition between the end plates, which usually is manufactured of carbon steel, and the two parts is eliminated.
Furthermore, such a first part, which has a larger material thickness than the second part, permits that the second part during the welding is pressed against the first part so that possible air, and thus oxygen gas, between the parts is forced away. Consequently, the need of so called root gas, i.e. the supply of an inert gas, for instance argon, for displacing oxygen gas from this welding area is eliminated.
Each of the two parts may be manufactured in one single step of manufacturing without any intermediate heat treatment. The time for the mounting of the lining device to the end plate is very short and the weld joint may advantageously be applied in an automatic manner.
According to an embodiment of the invention, the sheet metal of the first part has a thickness, which is larger than 1,5 mm at least at said overlapping area. Such a thickness is sufficient for preventing contamination of the material and for resisting the forces applied in connection with the above-mentioned pressing of the parts against each other.
According to a further embodiment of the invention, the weld joint extends around substantially the whole pipe portion of the first part. Furthermore, the pipe portion of the second part may have a first end, which is introducible in the pipe portion of the first part, wherein the weld joint is applied at said first end.
According to a further embodiment of the invention, the abutment portion of one of the first part and the second part is arranged to form an outer abutment portion and to abut the outer side of the end plate, and the abutment portion of one of the second part and the first part is arranged to form an inner abutment portion and to abut the inner side of the end plate, wherein the material thickness of the outer abutment portion is larger than the material thickness of the inner abutment portion. The outer abutment portion may then have an outer side, which faces away from the plate package and which includes at least one depression, for instance one or several grooves, for receiving a sealing element between said outer side and a pipe connection, wherein the sealing element may be pressed against said outer side in a secure and reliable manner. Advantageously, the abutment portion of the first part is shaped as a flange portion, which extends around the pipe portion and substantially radially outwardly from the pipe portion, and the abutment portion of the second part is shaped as a flange portion, which extends around the pipe portion and substantially radially outwardly from the pipe portion.
According to a further embodiment of the invention, the pipe portion of the first part is introducible into said porthole from the outer side of the end plate and the pipe portion of the second part is introducible in said porthole from the inner side of the end plate. Such an embodiment is advantageous and permits the manufacturing of the first, outer part in one single piece of material with a relatively large material thickness and the second inner part in one single other piece of material with a relatively small material thickness.
The object is also obtained by the plate heat exchanger initially defined, which is characterised in that the material thickness of the first part is larger than the material thickness of the second part at least at said overlapping area.
Furthermore, the object is obtained by the initially defined method, which includes the steps of:
providing a first part, which is manufactured of a sheet metal with a material thickness and which has a substantially cylindrical pipe portion and an abutment portion,
providing a second part, which is manufactured of a sheet metal with a material thickness and which has a substantially cylindrical pipe portion and an abutment portion,
introducing the pipe portion of the first part in said porthole,
introducing the pipe portion of the second part in said porthole in the pipe portion of the first part in such a manner that an area is formed where said pipe portions overlap each other, wherein the material thickness of the first part is larger than the material thickness of the second part at least in said overlapping area, and p1 connecting the pipe portion of the second part to the pipe portion of the first part by the application of a weld joint.
Preferred embodiments of the method are defined in claims 12 to 15.